Method for protecting a cooker extractor hood against overheating

ABSTRACT

The invention relates to a method as well as a device to protect against overheating in a cooker extractor hood ( 1 ) over a cooker ( 7 ) with at least one fan device ( 4 ) and with at least one temperature sensor ( 5, 6 ). To this end the method includes the steps of detection of a temperature by the temperature sensor ( 5, 6 ); when a first temperature threshold is reached or exceeded (level 1) of increasing the blower output ( 4 ); when a second temperature threshold is reached or exceeded (level 2) of presentation of a second warning signal, and when a third threshold is reached or exceeded (level 3) of switching off the blower device ( 4 ).

The present invention relates to a method as well as a device for protecting a cooker extractor hood mounted above a cooker against overheating, with at least one blower device and with at least one temperature sensor.

Because of the high temperatures at which they operate, cookers are generally a major source of danger in the kitchen. A cooker or cookers left unattended operating continuously at high power heat up the rising air, which is generally extracted using extractor hood devices. In such cases all components of the cooker extractor hood become very hot, especially the filters arranged within them. Most cooker extractor hoods have a grease filter in which the grease from the vapor rising from the cooker is collected. The combination of the grease becoming very hot and the effects of fire or an electrical spark can lead to the grease catching light.

A cooker extractor hood as a well as a method for protecting against fire in a cooker extractor hood above a cooker is described in U.S. Pat. No. 3,690,245. According to this two temperature sensors are provided upstream of a blower device of the cooker extractor hood for protecting against fire in the grease filter. The first detects a temperature of 60° C. (140° F.). If the air flowing through the cooker extractor hood reaches this temperature, the blower device is switched on automatically, provided this has not already been done in manual operation. The second sensor detects a temperature of 116° C. (240° F.). If the air flowing through the cooker extractor hood reaches this high temperature level, the blower device is automatically switched off, and a warning signal shows that the blower has stopped.

A disadvantage of this known method lies in the fact that this is only a purely automatic safety circuit for maximum loads. The user of such a device is not given any information about the high temperature prevailing so that he is not able to take any action in advance to counter a thermal overload. The user is only informed after a maximum load about the automatic intervention into manual operation.

The object of the present invention is thus to create a protection circuit or a cooker extractor hood with a protection circuit which makes it possible to avoid thermal overloads of the cooker extractor hood.

In accordance with the invention this object is achieved by a method with the steps of detection of a temperature by the temperature sensor; if a first temperature threshold is reached or exceeded (level 1), setting the blower device to a higher power; if a second temperature threshold (level 2) is reached or exceeded, displaying a warning signal and, if a third temperature threshold (level 3) is reached or exceeded, switching off the blower device, as well as by a suitable cooker extractor hood for executing this method.

The method as claimed in the invention is used to avoid cooker hood extraction fires on the one hand and to avoid damage to the cooker extractor hood on the other hand. Especially with cookers having a number of cooking zones and in particular with cookers with four to six gas burners, the heat developed by the cooker is significant. This heat generated reaches the extractor hood arranged over the cooker as the vapor rises. Cooker extractor hoods nowadays have one of more filters, which filter grease out of the vapor for example. This involves a danger of fire with very high thermal loading.

Warning signals in the sense of the invention are visual or acoustic signals with a more or less penetrating indication for the user of the cooker. Basically they act as an indication of a situation in which the danger arising from said situation can be averted by intervention on the part of the user. To this end the warning signals are such that it is possible to distinguish between an indication and an emergency warning.

The delivery of a higher blower power in the sense of the invention means a higher volume transport per unit of time by comparison with the volume transport set before the first temperature threshold was reached. Generally this is achieved by a higher speed of the ventilator in the blower. The higher speed can however in its turn lead to a temperature increase in the cooker extractor hood.

Reaching or exceeding a temperature threshold can simply mean the detection of a predetermined threshold temperature by a sensor. It is however also within the sense of the invention for the temperature threshold to include further components as well as the temperature component.

The inventive method in accordance with the invention is undertaken at level 1 and 3 as an automatic intervention into the manually predetermined operation of the cooker extractor hood. The intervention of the overheating protection device into manual operation can be ended after changes to conditions in the sense of the invention or can also be continued.

The object of the present invention is achieved by the inventive method or inventive protection device by enabling thermal overloads of the cooker hood to be avoided.

In one embodiment of the method this includes the steps of detection of a temperature by the temperature sensor; when a first temperature threshold (stage 1) is reached, setting the blower device to a higher power and if necessary additionally the display of a first warning signal; when a second temperature threshold is reached or exceeded (level 2) display of a second warning signal, and when a third threshold is reached or exceeded (level 3) switching off the blower device and if necessary additionally at least one area the cooking zone and where necessary additionally the display of a third signal. In this case the method at level 3 is undertaken as an automatic intervention of the overheating protection device emanating from the cooker extractor hood in the manual preset operation of the cooker. Here too the intervention of the overheating protection device into manual operation can be ended or can be continued once conditions have altered in the sense of the invention.

Preferably the first warning signal is an optical indication, especially preferably an indication of an increased temperature in the cooker extractor hood. For example a signal lamp lights or another optical indication is issued in the form of a text over the warning. The advantage of such a warning signal, which is easily and securely recognizable but still able to be further escalated and not recognizable as an emergency warning, lies in the fact that the user notes a higher temperature in the cooker extractor hood. The user can then react accordingly and for his part take action to counter a disproportionate temperature load, by switching off a cooker for example.

Expediently the second warning signal is reproduced in the form of an acoustic and/or visual indicator, especially an indication of the danger of fire. But aside from the acute danger of a fire, an acute danger can arise from components, especially plastic components, in the cooker extractor becoming soft when overheated as a function of temperature and changing their shape, in which case the function of the cooker extractor hood can no longer be guaranteed. This can be indicated acoustically or optically, for example by a significant red light, especially a flashing light and/or a text field with the information about an acute danger. Especially preferably a shrill or penetrative tone or sequence of tones sounds, which causes the user—who may possibly be absent for a few moments—to take action to counter the danger and may cause him to hurry to do so. The signal of the second stage is such that this is to be perceived uniquely as an emergency warning. This gives the user the option of being able to intervene even before a thermal overload of the cooker extractor hood occurs and take action to counter a danger.

It is useful for the third signal to be an acoustic and/or optical indicator, especially an indication that a maximum temperature has been reached and/or of the deactivation of the operation of the cooker extractor hood and/or of the cooker. For example the indication is given by a signal lamps or another form of optical indication, especially of a text about the warning. The advantage of such an easily and securely detectable warning signal, but still not one recognizable in the sense of an emergency warning signal, lies in the user recognizing the reason why the cooker extractor hood is no longer in operation. The user can then react correspondingly and where necessary check the functions of the cooker extractor hood before putting it back into operation.

It is deemed expedient for the corresponding first or second warning signal to be extinguished again once the temperature subsequently drops below the first or second temperature threshold. The warning signals of level 1 and 2 are signals in the sense of allowing the user for their part to take precautions to avoid overloads. A rise in the temperature detected at the sensor indicates that a thermal overload temperature is being approached. If on the other hand the temperature falls, there is no direct danger of overload, so that the user initially does not have to take any precautions or may possibly already have taken precautions. The advantage of such an extinction of the warning signals lies in the fact that the indication of such a situation only appears at the instant of an impending overload, i.e. when the situation becomes acute, but does not however remain for a past impending danger situation.

It is also deemed expedient, when the temperature subsequently falls below a first and second temperature threshold, for the blower power to be reduced to its original state before the temperature increase. If the temperature falls, there is no direct danger of overload, so that initially no precautions have to be taken. The advantage of such a graduated reduction of the blower power lies in the fact that only at the moment of the impending overload, i.e. in the acute case, is the blower power set to this level, but is not maintained however for a past impending danger situation. This saves energy and does not confuse the user.

In a further embodiment there can be provision for, even after the temperature falls below a third threshold, the blower device and preferably the at least one cooking zone to remain switched off. To protect the cooker extractor hood and especially to counter a danger of fire in the grease filter the blower device is switched off. This state is maintained because of the acute danger of fire, and the blower device is not put back into operation. The high temperature in the cooker extractor hood can thus be gradually reduced. To support this, at least one area of the cooking zone is switched off and remains switched off. This ensures that the energy output of the heat sources has been reduced and will be increased again without having been checked by the user.

In a further embodiment provision is expediently made for a third signal to be displayed even after the temperature has fallen below the third threshold. Thus the user is informed that a thermally critical state of the cooker extractor hood was reached, which, although it obviously did not lead to a fire, could possibly have left behind damage to the cooker extractor hood. When the cooker extractor hood is put back into service, the user is caused by the signal to check the correct functioning of the cooker extractor hood and thus to pay increased attention to the device.

As well as a temperature component, the respective temperature threshold can also include a time component, so that the temperature threshold is defined by the prevalence of a predetermined first, second or third temperature for a predetermined time. This avoids one of the levels being activated solely by a temperature threshold being exceeded for a short time. For example during the process of flambéing a short but high thermal load is imposed on the cooker extractor hood. Since this is a usual cooking process, the cooker extractor hood can be designed to withstand these short heat effects without danger. Accordingly no indication of a source of danger is required, but only after longer effects of heat over time, such as for example over 30 seconds, or over one or two minutes. Thus the case can occur in which, when the third temperature threshold is reached or exceeded quickly, levels 1 and 2 can be skipped, since the temperatures of these thresholds are only briefly reached as a result of the rapid temperature increase. Increased heat developing and effecting the cooker extractor hood can be established by the at least one sensor and thus for example a distinction can be drawn between a permanent heating up by the operation of a number of cooking zones, a flambéding process and a fire. Levels 1 and 2 are skipped in the case of a detected fire, especially so that the increase in the fan output does not feed the fire further, but this effect is countered by the immediate switching-off of the blower.

In a further aspect of the invention this provided an overheating protection device—referred to below as a protective circuit—for a cooker extractor hood over a cooker with at least one blower device and with at least one temperature sensor, which is suitable for executing the method described above.

It is expedient for at least one temperature sensor to be arranged in an extraction area and/or in a fan flow of the cooker extractor hood. In addition to the danger of a grease filter fire there is also the danger of deformations of the air ducts. For example the air ducts can be formed at least partly from plastic and deform if subjected to very high thermal loads. These deformations adversely affect the function of the cooker extractor hood and can give rise to a danger the hot air being routed not through the specified duct but onto a sensitive component such as for example the electrics of the cooker extractor hood. Thus the temperature is measured especially in an area upstream of the components, such as fan housing and exhaust duct, especially in the induction area and/or in the fan air flow. Preferably two or three sensors are provided in this area to allow a more precise detection of the temperature states of the individual components.

It is advantageous for the cooker extractor hood to include a measured value memory. Especially with regard to the embodiment of the temperature with a timing component (as described above) the detectable temperature values can thus be established using a timing curve. There is provision in a further development for the protective device of the cooker extractor hood to have a control and regulation unit, preferably a programmable control and regulation unit. Thus individual parameters, for example the temperature thresholds with timing components, can be individually adapted to the respective cooking zone and cooking habits of the user.

Preferably the cooker extractor hood is connected to the cooker, especially preferably electrically. To switch off at least one cooking zone of the cooker at the third level there is a connection between the protection device of the cooker extractor hood and the cooker. This connection can be implemented by a wire or wirelessly so that signals can be sent from the cooker extractor hood to the cooker. In the case of an electric cooker at least one cooking zone is electrically switched off, in the case of a gas cooker, a valve, preferably a magnetic valve, can be provided in the gas supply to the gas cooker. The valve is electrically controlled accordingly and shuts off the gas supply, so that the heat directed to the cooker extractor hood is reduced.

Higher thermal loads particularly occur in the embodiment in which the cooker is embodied as a gas cooker. For example the cooker includes four or up to six individual gas burners under the cooker extractor hood which, at maximum power, cause a very large amount of heat to be generated in the air fed to the cooker extractor hood. The additional removal of a pot or a pan, with a gas burner continuing to output heat at the same time, again causes a noticeable increase in the thermal load. In such a case an overload of the cooker extractor hood can occur simply through normal cooking operation.

The present invention will be explained below with reference to the enclosed drawings. The figures show:

FIG. 1: a schematic front view of an inventive cooker extractor hood with overheating protection device above a cooking zone;

FIG. 2: a flowchart of the inventive overheating protection device of the cooker extractor hood; and

FIG. 3: a schematic diagram of the inventive protection circuit (overheating protection device) of the cooker extractor hood;

FIG. 1 shows a front view of an inventive cooker extractor hood I with grease filter 2, a fan duct 3 and a blower unit 4. The cooker extractor hood 1 includes two temperature sensors 5 and 6, with one sensor 5 being arranged in the induction area in the direction of flow in front of the grease filter 2 and the other sensor 6 in the fan duct 3 behind the grease filter 3. Under the cooker extractor hood 1 a gas cooker is provided as the cooker 7 with four burners 8.

In this case each of the four gas burners 8 has a maximum power of around 4000 W, corresponding to around 15,000 BTU. Set together and simultaneously to full power output these can generate such a high level of heat over a long period below the cooker extractor hood 1 that for example the plastic fan duct 3 is deformed. This is especially the case if food is also being flambéd or a pot or a pan is removed from one of the burners 8 without restricting the power output, so that the full intensity of the heat developed can rise into the cooker extractor hood 1.

One temperature sensor 5 is arranged in the induction area and one temperature sensor 6 in the area of the fan duct 3 of the cooker extractor hood 1 respectively. The sensor 5 in the induction area is used for measurement of the temperature of the air flowing into the cooker extractor hood. This enables feedback to be provided on the state of the grease filter arranged beyond the sensor and the grease drawn into this filter 2. In addition to the danger of fire in the grease filter 3 there is also the danger of deformation of the air ducts 3. Since the air ducts 3 are formed at least partly from plastic and are deformed by very high thermal loads, these deformations can adversely affect the function of the cooker extractor hood 1 and as a result of a changed routing of hot air onto sensitive components such as the electrics for example of the cooker extractor hood 1 for example, can be give rise to danger. Thus the temperature is also measured in the fan duct 3 with a second sensor 6. The invention is not restricted to the number of sensors shown, instead a higher number of sensors produce a more precise ability to determine the temperature of the individual critical areas such as the grease filter 2 and the fan duct 3.

To reproduce warning signals, a display with flashing lights 13 and a variable text field 14 is provided on the front of the cooker extractor hood 1 at about the eye level of the user.

FIG. 2 shows a schematic diagram of a flowchart of the inventive method to protect against the cooker extractor hood 1 overheating. Starting from a basic state in the cooking operation, in which the cooker extractor hood 1 is set for example through manual activation to a specific fan output, the protection device comes into force when a first temperature level 1 is exceeded as a first warning level of the protective device.

In addition to a temperature component, each temperature threshold also includes a timing component, so that the temperature threshold is defined by the predominance of a predetermined temperature for a predetermined time. This avoids one of the levels being activated solely by a temperature threshold being exceeded for a short time. This means that in the flambéding process the short but very high thermal load exerted on the cooker extractor hood cannot be sufficient to put the protection device into a warning level. The method in accordance with the invention recognizes the process as a normal process during cooking and does not indicate any danger situation, but only after the heat has been in effect for a longer period, such as over 30 seconds for example, or over one of two minutes, if the grease in the grease filter 2 or plastic parts in the fan duct 3 would be heated up to dangerously high levels.

If the case now arises in which the first temperature threshold—of a predetermined first temperature is reached or exceeded for a likewise predetermined time—then at level 1 a first warning signal appears in the form of an optical indication. A warning light 13 flashes in the display 9 and if necessary a text indication 14 also appears as an easily and securely detectable warning, but one that is still able to be further escalated and is not recognizable as an emergency warning. The user can thus be aware of an increase in temperature in the cooker extractor hood 1. The user can react to this in an appropriate manner and for his part take action to counter a disproportionate temperature load, by switching off an individual gas cooker burner 8 for example. Regardless of this, when the first warning level is activated, the blower device is automatically set to a higher blower power than that set previously. Thus the heat generated under the cooker extractor hood 1 is removed so that a heat buildup does not occur. The cooler air sucked in additionally from the border areas of the warm rising vapor make possible a temporary reduction of the temperatures in the cooker extractor hood 1.

If the second temperature threshold—likewise of a predetermined temperature is reached or exceeded for a predetermined time, warning level 2 comes into force.

A second possibly additional warning signal in the form of an acoustic indicator occurs. This is a more high-pitched and shriller tone or a sequence of tones which occurs as a pulse. The signal of the second level is such that this is clearly perceived as an emergency warning. In addition the display 9 of the visual indication of a danger of fire may appear in the text field 14. This gives the user the opportunity of being able to intervene even before the occurrence of a thermal overload of the cooker extractor hood 1 and counter a danger.

If the third temperature threshold is now reached or exceeded, level 3 comes into force as a warning and especially as a safety level. To this end the blower device 4 is switched off. Furthermore at least one cooking zone 8 of the cooker 7 is deactivated. A circuit designed as a safety circuit switches off all gas burners 8. The burners are switched off by means of an electrical signal to a magnetic valve or to at least one magnetic valve 12 (shown in FIG. 3) in the area of gas supply to the gas burners 8. In addition a signal in the form of an optical indicator appears when a maximum temperature has been reached when the operation of the cooker extractor hood 1 has been deactivated. The indication is provided on the one hand by the flashing of a signal lamp 13 and if necessary by an additional text indication 14 of the display 9. The user can then react accordingly and where necessary check the functions of the cooker extractor hood before putting it back into operation.

The invention is not restricted to a warning signal 13 in combination with text information 14. The text information can optionally be omitted, so that it is possible for the user to recognize from a suitable choice of the respective signal which intervention the automatic circuit of the overheating protection device has made into manual operation.

After the temperature subsequently falls below the third temperature threshold the blower device 4 and the individual gas burners 8 of the cooking zone 7 remain switched off. To protect the cooker extractor hood and especially to counter a danger of fire in the grease filter 2 the blower device 4 is switched off. This state is maintained because of the acute danger of fire, and the blower device is not put back into operation. This ensures that the energy output of the heat sources has been reduced and will not be increased again without being checked by the user.

After the temperature subsequently falls below the third temperature threshold the third signal continues to be displayed. Thus the user is informed that a thermally critical state of the cooker extractor hood was reached, which, although it obviously did not lead to a fire, could possibly have left behind damage to the cooker extractor hood. When the cooker extractor hood is put back into service, the user is prompted by the signal to check the correct functioning of the cooker extractor hood and thus to pay increased attention to the device.

After the temperature subsequently falls below the first or second temperature threshold the corresponding first or second warning signal is extinguished again. The warning signals of level 1 and 2 are signals indicating that the user for his part can take precautions to avoid overloads. If the temperature falls again, there is no direct danger of overload, so that the user initially does not have to take any precautions or may possibly have already taken precautions.

Furthermore, after the temperature has fallen below the first and second temperature threshold the blower power is reduced to its original level before it was increased.

If the temperature suddenly reaches or exceeds the third temperature threshold, i.e. if the temperature passes rapidly through the temperature thresholds below the respective predetermined timing components of level 1 and 2, levels 1 and 2 can be skipped. If a sudden development in the increase in heat affecting the cooker extractor hood 1 is established by means of the two sensors 5, 6, which was caused by a fire for example, the blower 4 will be switched off immediately. The protection circuit can thus distinguish between an ongoing heating up by the operation of a number of burners 8 and a fire. If a fire is detected levels 1 and 2 are skipped, especially so that the increase in the blower output does not feed the fire further; instead this effect is countered by the immediate switching-off of the blower.

FIG. 3 shows a schematic diagram of an inventive protective circuit of the overheating protection device in the cooker extractor hood. To this end two temperature sensors 5 and 6 are provided, which each transmit the measured values to a measurement data memory 10. The measurement data is forwarded to a control unit 11 which in its turn is electrically connected on the one hand to blower 4 of the cooker extractor hood and on the other hand to magnetic valves 12 in the gas supply to the individual gas burners 8.

The circuit arrangement of the overheating device is not restricted to the embodiment shown in FIG. 3. For example each sensor 5, 6 can send the data to a measured value memory 10. Alternatively the measurement data memory can also be only directly connected to the control unit 11 or if necessary also omitted. 

1-17. (canceled)
 18. A method for protecting a cooker extractor hood mounted above a cooker against overheating, with a blower device and a temperature sensor, the method comprising: detecting a temperature with the temperature sensor; increasing the blower power when the temperature reaches or exceeds a first temperature threshold; displaying a warning signal when the temperature reaches or exceeds a second temperature threshold; and switching the blower device off when the temperature reaches or exceeds a third temperature threshold.
 19. The method of claim 18 and further comprising displaying the warning signal when the temperature reaches or exceeds the first temperature threshold.
 20. The method of claim 19, wherein the warning signal comprises an optical indication of an increased temperature in the cooker extractor hood.
 21. The method of claim 18, wherein the warning signal comprises an acoustic or visual indication of a danger of fire.
 22. The method of claim 18 and further comprising displaying another warning signal when the temperature reaches or exceeds the third temperature threshold.
 23. The method of claim 22, wherein the another warning signal comprises an acoustic signal or an optical indication that a maximum temperature has been reached or of the deactivation of the operation of the cooker extractor hood.
 24. The method of claim 22, wherein the another warning signal continues to be displayed after the temperature subsequently falls below the third temperature threshold.
 25. The method of claim 18 and further comprising extinguishing the warning signal when the temperature falls below the second temperature threshold.
 26. The method of claim 18 and further comprising switching off an area of the cooker when the temperature reaches or exceeds the third temperature threshold.
 27. The method of claim 18, wherein the blower devices remains switched off when the temperature subsequently falls below the third temperature threshold.
 28. The method of claim 18, wherein said reaching or exceeding one of the first temperature threshold, the second temperature threshold, and the third temperature threshold is defined by reaching or exceeding a temperature threshold for a predetermined time.
 29. An overheating protection device for a cooker extractor hood mounted above a cooker with a blower device and a temperature sensor, the device comprising: means for detecting a temperature with the temperature sensor; means for increasing the blower power when the temperature reaches or exceeds a first temperature threshold; means for displaying a warning signal when the temperature reaches or exceeds a second temperature threshold; and means for switching the blower device off when the temperature reaches or exceeds a third temperature threshold
 30. An overheating protection device, comprising: a temperature sensor that provides a temperature signal; a blower controller responsive to the temperature signal reaching or exceeding a first temperature to increase a power to a blower device; a warning signal display that displays a warning when the temperature signal reaches or exceeds a second temperature threshold, wherein the blower controller is further responsive to switch the blower off when the temperature signal reaches or exceeds a third temperature threshold.
 31. The device of claim 30 and further comprising a measured value memory.
 32. The device of claim 30 wherein the temperature sensor is positioned in an induction area or a fan duct of a cooker extractor hood.
 33. The device of claim 30, wherein the cooker extractor hood is mounted above a cooker and wherein the overheating protection device is electrically connected to the cooker.
 34. The device of claim 33, wherein the cooker comprises a gas burner.
 35. The device of claim 34 and further comprising a gas supply to the gas burner that comprises a valve. 